Drive mechanism for vacuum switches



April 26, 1966 w. N. LINDSAY 3,243,497

7 DRIVE MECHANISM FOR VACUUM SWITCHES Filed m. 9, 1961 2 Sheets-Sheet 1 1N VENTOR.

WESLEY N L /ND$AY ATTORNEY April 26, 1966 w. N. LINDSAY 3,248,497

DRIVE MECHANISM FOR VACUUM SWITCHES Filed 001;. 9, 1961 2 Sheets-Sheet 2 1N VENTOR.

WESLEY N LINDSAY A T TORNEY United States Patent 3,248,497 DRIVE MECHANISM FOR VACUUM SWITCHES Wesley N. Lindsay, San Jose, Calif., assignor to Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of Delaware Filed Oct. 9, 1961, Ser. No. 143,638

12 Claims. (Cl. 200-87) This invention relates to a drive mechanism for vacuum switches and has as its main object the provision of a drive mechanism which permits extremely fast opening and closing movement of the movable contact and which at the same time minimizes the undesirable effects nor-.

mally attending high speed opening and closing movement of such vacuum switches.

Another object of the invention is the provision of a drive mechanism for vacuum switches in which a relatively high holding force is developed to retain the movable contact in engagement with the fixed contact thereby minimizing the undesirable effects resulting from the movable contact bouncing away from the fixed contact. This object is promoted by the additional provision of means for reducing the velocity of the movable contact just before contact with the fixed contact so as to reduce impact and the resulting bouncing efiect.

Another object of the invention is the provision of a relatively simple and inexpensive means for providing 'quick closing in a vacuum switch and which means remains effective throughout a relatively large number of actuations of the switch.

Other objects of the invention will be apparent from the following specification and from the drawings. It will be understood, of course, that the particular embodiment of the invention shown in the drawings and described in the specification should not be taken as restrictive of the invention since various modifications in design will occur to those skilled in the art without departing from the scope of the appended claims.

FIG. 1 is a side elevation, partly in section and partly broken away for clarity, of a vacuum switch and drive mechanism incorporating the present invention. The parts are shown in a position intermediate the open and closed positions.

FIG. 2 is a sectional view of the holding means, taken in a plane indicated by the line 2-2 of FIG. 1.

FIG. 3 is a vertical section through the driving means, taken in a plane indicated by the line 33 of FIG. 1.

FIG. 4 is a fragmentary view similar to FIG. 1 showing the drive mechanism and switch contacts in closed position.

FIG. 5 is a fragmentary view similar to FIG. 1 showing the drive mechanism and switch contacts in open position.

In vacuum switches of the type herein contemplated proper design must provide for rapid movement of the movable contact into engagement with the fixed contact and at the same time the actual terminal velocity of the movable contact must be sufliciently low so that impact between the contacts is reduced as much as possible. By the present invention such requirements are adequately provided for by the provision of resilient means automatically controlling the movement of the movable contact throughout its stroke.

Referring first to FIG. 1 the invention is illustrated in connection with a vacuum switch which includes an envelope 1, a fixed contact 2 and a movable contact 3. The latter is carried by a rod 4 which extends to the outside of the envelope and is provided with a threaded portion 5. For the purpose of maintaining a vacuum within envelope 1, and at the same time permitting movement of rod 4, bellows 6 is provided with one end secured "ice to rod 4 and the opposite end to mount 7, to which the envelope 1 is also secured. y

The drive mechanism to be subsequently described may be conveniently arranged in a housing having a bottom wall 10, side walls 11, 12 and top wall 13. The mount 7 for envelope 1 is secured to top wall 13 which may be suitably apertured to receive rod 4 thercthrough.

Threaded on portion 5 of rod 4 is a circular plate 15 against which abuts the lower end of a compression spring 16. The opposite upper end of the spring engages the underside of top 13. The exact operation of spring 16 will subsequently be explained in greater detail, but at this point it may be noted that the spring is under compression and urges the movable contact 3 away from fixed contact 2 at all times.

Carried by the threaded portion 5 of movable contact rod 4.is an elongated clevis 18, including opposed plates 19, 20 between which extends a pin 21 for rotatably supporting a roller 22. Y

, Roller 22 operates within a slot 25, formed in a generally triangular shaped cam plate 26, pivotally supported adjacent its lower end on a pin 27 which in turn is fixedly secured to an elongated lever 28, intermediate the ends of the latter. Lever 28 is pivotally supported at one end on pin 29, carried by bracket 30, fixed to bottom wall 10. The opposite end 31 of lever 28 is free; except that means, subsequently to be described, are provided for automatically holding this end in fixed position for a period during operation of the device. Vertically extending elongated slots 17 are provided in plates 19, 20 of clevis 18 to permit vertical movement of clevis 18 relative to cam 26.

The free end 31 of lever 28 is urged upwardly at all times by a compression spring 32 which is interposed between lever 28 and the bottom 10 of the housing. At this point it is noted that the pressure of spring 32 is imposed through lever 28, pin 27, cam plate 26, roller 22, clevis 18 and rod 4 to urgemovable contact point 3 into engagement with fixed contact 2.

Referring again to cam slot 25 in carn plate 26, it will be noted that the shape of slot 25 is predetermined so that when cam plate 26 is swung to the right about pivot 27, to the position shown in FIG. 4, roller 22 is driven upwardly, thereby carrying movable contact 3 into engagement with fixed contact 2. If cam plate 26 is swung to the left from its position shown in FIG. 1 to the position shown in FIG. 5, the movable contact 3 is moved away from fixed cotnact 2.

In order to insure movement of clevis 18 and rod 4 along a substantially straight line of action, the lower ends of plates 19, 2t) of the clevis are provided with elongated slots 17 which provide slide bearings for the clevis on opposite ends of pin 27, which is fixed in the lever 28.

For the purpose of urging the movable contact point 3 to an open position, a tension spring 37 is provided, one end of which is secured to sidewall 11 and the other end to a pin 38 carried by cam plate 26. For closing the switch a solenoid 40 is fixed on side wall 12; and its plung-- er 41 is secured to one end of a link 42, while the opposite end of the link is pivoted to pin 38 on cam plate 26. It will be apparent that when solenoid 40 is energized, the cam plate 26 swings to the right as in FIG. 4, to close the switch contacts 2, 3.

Solenoid 40 may be energized through leads 43, 44 connected respectively to power lines 45, 46. A switch, such as push button 47 in line 43, may be employed to control the actuation of solenoid 40.

Fora purpose to be described it is desirable to be able to hold against movement the free end 31 of lever 28, and for this purpose a member generally designated 50,

is fixed on bottom wall of the housing. This member includes a pair of upstanding lugs 51, 52; and lever 28 is arranged to lie alongside lug 51 as best seen in FIG. 2. A locking plate 53 is movably arranged on the member 50 at the side of lever 28 opposite to lug 51, and is forceably urged into frictional engagement with lever 28 by one end of a strong compression spring 54 which at its opposite end abuts the lug 52. A solenoid 55 is arranged within the coils of spring 54, and when energized, retracts pressure plate 53 from the free end of lever 28 so that the latter is released from its clamped engagement between the pressure plate and lug. Solenoid 55 may be energized through leads 56, 57 from power lines 45, 46.

It is desirable to energize solenoid 55 to release the free end oflever 28 whenever the switch closing solenoid 40 is energized. For this purpose a switch 59 is provided having one switch arm 60 engageable by solenoid plunger 41 as the latter moves to its vacuum switch closing position. It is therefore apparent that when switch contacts 2, 3 are open and cam plate 26 is swung to the left by spring 37, the holding device shown in FIG. 2 clamps the free end of lever 28. However when solenoid 40 is energized to close the vacuum switch, solenoid 55 is energized to release lever 28 and thereby permit the spring 32 to act on the movable switch contact 3, so that independent of the movement of the roller 22 in the cam slot, the slight amount of wasteage occurring at the contact points is compensated with each operation.

The above described structure permits the movable contact point 3 to move from an open position to a closed position with optimum speed, and at the same time the tendency of the movable contact to bounce clear of the fixed contact after impact is minimized. To achieve this desirable object, it is of course, necessary to select the spring 16 and the other yieldable elements referred to above so as to take into account other variables present.

In this connection it will be noted that forces are im pressed upon mobile contact 3 by the following: the atmosphere, bellows 6, spring 16, cam 26 and spring 32. Spring 32 may be disregarded insofar as the dynamic forces acting on the mobile contact 3 are concerned because this spring does not contribute to the force on fixed contact 2 except when the contacts are closed. In other words, while the contact actuating mechanism is working lever 28 is fixed in place by pressure plate 53.

Since cam 26 dictates an exact predetermined travel of mobile contact 3 the only elements remaining to affect the loading on said mobile contact are: the atmosphere, bellows 6 and spring 16. Of these three sources of loading only bellows 6 and spring 16 are variable in effect, the atmospheric pressure being assumed to be constant.

To avoid fatigue failure of bellows 6 the same should be designed so as to undergo very little strain during actuation of the switch and while it is at rest. Preferably bellows 6 should be in an unstressed condition when the contacts are closed in which case it is under a small amount of compression when the switch is open and thus bellows 6 is always urging the contact 3 to closed position. However, spring 16 is relatively strong and of course is compressed by plate to provide an initial compression even in its extended condition when the switch contacts are open.

As a particular example of an operative combination which achieves the desired result, the spring 16 may be of a size to provide a spring constant of 60. Assuming the total travel of mobile contact 3 to be A", the spring 16 r ng therefore be setto impose a load tending to open the contacts of 30 pounds when the contacts are in closed position and a load of 15 pounds when the contacts are open. If the spring constant of bellows 6 is 20 and it is unstressed when the switch is closed it will be under a loading of 5 pounds tending to close the contacts when the switch is open. Further assuming that the cross sectional extent of bellows 6 is such that atmospheric pressure exerts a load of 20 pounds thereon it will be apparent that the total force acting on the mobile contact at any one time, aside from cam 26, will be the algebraic sum of the forces represented by the atmosphere, bellows 6 and spring 16. Since the bellows and atmosphere act in closing direction and spring 16 acts in an opening direction, it will be apparent that the total force on contact 3 when the same is open will be 10 pounds and said total force will act to close the contacts. Similarly, in the example given, the total forces tending to open the contacts when they are closed will be 10 pounds.

It is therefore apparent that a yieldable resistance is imposed on contact rod 4 in opposition to the load imposed by cam 26. In other words, as cam 26 is moved to the left from the position of FIG. 4 toward the position of FIG. 5 the above described assembly resists said movement with a load diminishing from 10 pounds to zero as said cam moves toward the intermediate position of FIG. 1. The assembly then resists movement from the neutral position of FIG. 1 toward the position of FIG. 5 with a force increasing from zero to 10 pounds.

The above quantitative example of the pertinent forces assumes no effect of spring 32 being present. This assumption is justified because spring 32 acts only to impose a load on mobile contact 3 against fixed contact 2 when the contacts are closed. This, of course, is desirable. However, as noted above, when the driving mechanism is being actuated, lever 28 is fixedly secured in place by pressure plate 50 (FIG. 2) and its effect may therefore be disregarded insofar as the dynamic effects are concerned.

Returning again to the specific example set forth above it is seen that the assembly of bellows 6, spring 16 and including the effect of the atmosphere, the algebraic sum of the forces acting on mobile contact 3 amounts to 10 pounds assisting opening movement of the contacts in the position of FIG. 4; zero in the intermediate position of FIG. 1; and 10 pounds resisting opening movement of the contact in the position of FIG. 5. Since the assembly, in effect, moves A2 inch as the loading thereon changes 10 pounds, it follows that the behavior of the entire assembly could be duplicated by one spring having a spring constant of pounds per inch. In such a case the spring would be arranged in an unstressed condition in the neutral position of FIG. 1 and would exert a force of 10 pounds toward such neutral position when deflected inch in either direction.

Since it is necessary to provide a vacuum in envelope 1 and to provide bellows 6 to maintain said'vacuum, the above described assembly, including spring 16 is required. However, the behavior of the forces acting on mobile contact 3 may be more easily imagine-d if-the equivalent single spring is considered. If cam 26 were not present it is apparent that deflection of the assembly from the neutral position of FIG. 1 and release of the same would result in harmonic oscillation of the assembly until friction brings it to the position of FIG. 1. At fully open and fully closed positions the velocity of mobile'contact 3 is zero. Thus, when the action of cam 26 is introduced as described above the same merely acts to guide the contact 3 through a predetermined travel and latch the assembly in fully open or fully closed position. At the point of closing the system provides an effective cushioning of contact 3 as it approaches fixed contact 2. Thus the object of reducing impact and the attendant rebound o f the mobile contact is achieved.

The importance of spring 32 acting on lever 28 will now be apparent. Since said spring 32 dictates the force with which mobile contact 3 engages fixed contact 2 -while the switch is in closed position it also defines the 70- starting point from which the driving assembly moves during its cycle from closed to open and back to closed position. Despite deterioration of the contacts and Wear in the various parts, spring 32 therefore insures that all cycles are identical and, more important, that the terminal velocity of the contact 3 as it closes always remains the same even after many cycles have taken place. Also spring 32 effectively holds the contacts in closed position.

An important feature of the instant invention resides in the fact that a substantial portion of the work required to move the mobile contact through its opening and closing cycles comes from energy stored in the resilient system that includes bellows 6 and spring 16. This follows from the fact that the assembly tends to move with harmonic motion from one extreme position to the other. The cam 26 and its actuators, that is spring 37 and solenoid 40, merely provide sufficient work to overcome the friction that is present in the system.

Naturally the design of spring 16 and bellows 6 must take into consideration the weight of the moving mass involved. Thus to arrive at the spring constant one may use the formula where =spring constant in pounds per inch W=weight of the moving mass T =time period g=acceleration of gravity When properly designed as above described the resonance of the spring combination insures optimum speed of switch closing and at the same time the terminal velocity of the movable contact as it engages the fixed contact is reduced to as low a speed as possible thereby minimizing the tendency of the movable contact to bounce off the fixed contact.

The above very specific description of the preferred embodiment of the invention is not to be taken as restrictive thereof as it obvious that various modifications in design may be resorted to by those skilled in the art without departing from the scope of the following claims.

I claim:

1. An actuator assembly for moving a mobile switch contact from full open position through an intermediate position and to closed position and vice versa and for selectively holding said mobile contact in one or the other of said open or closed positions comprising;

means including resilient means capable of harmonic oscillation connected to said mobile contact to move the same and said resilient means having no stored energy therein when said mobile switch contact is in intermediate position and static energy built up therein when said mobile contact is moved to either closed position or full open position, said built up energy upon release from either full open or closed positions moving the mobile contact toward the other position through the release of its built up static energy and conversion to kinetic energy,

cam means operatively connected to said mobile contact and movable therewith to hold said contact in one or the other of said open or closed positions,

and means including a motor operatively connected to said cam means to move said cam means to a holding position corresponding to one or the other of said fully open or closed positions of the mobile contact.

2. The combination according to claim 1, in which said mobile contact is non-resiliently held in said open position by said cam means and resiliently held in closed position by said cam means.

3. The combination according to claim 1, in which said resilient means includes a bellows responsive to atmospheric pressure urging said mobile contact toward closed position and a second resilient means urging said contact toward open position.

4. The combination according to claim 1, including spring means connects with said cam means to urge said cam means and said contact toward closed position after said contact has reached that position but not before. 5. The combination according to claim 1, in which lock means are provided locking said cam means and said contact in open position when said contact has reached that position but not before.

6. An actuator assembly for driving an element between first and second positions through an intermediate position comprising:

an extension integral with said element, first and second driving means connected to said extension and operable to move said element toward said first or second positions, respectively, and

means including resilient means capable of harmonic oscillation connected to said extension and the memher and said resilient means having no stored energy therein when it and the extension and member are in intermediate position and having static energy built up therein when either said first or seconddriving means moves said extension and element toward said first or second positions, said built up energy upon release from either said first or second positions moving the extension and member toward the other position through the conversion of its built up static energy into kinetic energy.

7. The combination according to claim 6, in which another resilient member is provided acting to urge said element away from said second position when said element is in said first position.

8. In a vacuum switch supported on a base, a vacuumized envelope and a switch element in said envelope mounted for movement between open and closed positions, an extension integral with said switch element and mounted for movement with said element along a line of action to positions corresponding to said open and closed positions of said element, a pivot supported on said base at a point along said line of action, a cam member swingably mounted on said pivot for swinging movement in a direction transversely of said line of action, a cam follower on said extension cooperating with said cam member for moving said element to different positions along said line of action corresponding to said transverse swinging movementof said cam member, and opening and closing driving means operable respectively to swing said cam member to positions corresponding to open and closed positions of said element.

9. The combination according to claim 8, in which said pivot is movably supported on said base and spring means are associated with said pivot to urge said pivot and said element toward closed position to resiliently hold said element in closed position regardless of wear of said element.

10. The combination according to claim 9, in which means are provided to hold said pivot stationary against the urgency of said spring when said element is in open position. i

11. The combination according to claim 10, in which said means to hold said pivot stationary against the urgency of said spring is operatively connected to said closing driving means whereby actuation of the latter effects release of said pivot by said holding means.

12. A switch operator for a vacuum switch responsive to atmospheric pressure comprising:

a base frame,

a contact rod journaled axially in the base frame to open and close the switch,

a fixed contact stationary relative to the base frame,

a bellows interposed between the contact rod and the base frame and responsive to atmospheric pressure urging the contact rod to close the switch,

a spring interposed between the contact rod and the base frame and urging the contact rod to open the switch against the urgency of said atmospheric pressure,

a cam pivotally supported on the lever intermediate its 7 ends and engaging the rider to move the contact rod to open position against the urgency of atmospheric pressure and to close the switch against the urgency of said spring,

a spring interposed between the lever and the base and biased to pivot the iever in a Contact closing direction,

means to pivot the cam on said lever,

and means normally holding the lever against mov ment when said switch contacts are open and acting in time with the cam-moving means to release the lever When the contacts are closed.

References Cited by the Examiner UNITED STATES PATENTS Kennedy 20 0-92 Hutchi son 200-87 Adelson 200-106 Getchell 200-87 McBrien et al. 200-87 Brown et al. 200-87 Koppelmann 200-92 Rigert 200-87 Frentzel 200-170 Jennings 200-144 5 BERNARD GILHEANY, Primary Examiner.

MAX L. LEVY, ROBERT K. SCHAEFER, Examiners. 

1. AN ACTUATOR ASSEMBLY FOR MOVING A MOBILE SWITCH CONTACT FROM FULL OPEN POSITION THROUGH AN INTERMEDIATE POSITION AND TO CLOSED POSITION AND VICE VERSA AND FOR SELECTIVELY HOLDING SAID MOBILE CONTACT IN ONE OR THE OTHER OF SAID OPEN OR CLOSED POSITIONS COMPRISING; MEANS INCLUDING RESILIENT MEANS CAPABLE OF HARMONIC OSCILLATION CONNECTED TO SAID MOBILE CONTACT TO MOVE THE SAME AND SAID RESILIENT MEANS HAVING NO STORED ENERGY THEREIN WHEN SAID MOBILE SWITCH CONTACT IS IN INTERMEDIATE POSITION AND STATIC ENERGY BUILT UP THEREIN WHEN SAID MOBILE CONTACT IS MOVED TO EITHER CLOSED POSITION OR FULL OPEN POSITION, SAID BUILT UP ENERGY UPON RELEASE FROM EITHER FULL OPEN OR CLOSED POSITIONS MOVING THE MOBILE CONTACT TOWARD THE OTHER POSITION THROUGH THE RELEASE OF ITS BUILT UP STATIC ENERGY AND CONVERSION TO KINETIC ENERGY, CAM MEANS OPERATIVELY CONNECTED TO SAID MOBILE CONTACT AND MOVABLE THEREWITH TO HOLD SAID CONTACT IN ONE OR THE OTHER OF SAID OPEN OR CLOSED POSITIONS, AND MEANS INCLUDING A MOTOR OPERATIVELY CONNECTED TO SAID CAM MEANS TO MOVE SAID CAM MEANS TO A HOLDING POSITION CORRESPONDING TO ONE OR THE OTHER OF SAID FULLY OPEN OR CLOSED POSITIONS OF THE MOBILE CONTACT. 